This invention relates to a signaling arrangement between a processor and a communication station and more particularly to such an arrangement wherein bidirectional signaling is achieved using reconstructed data messages.
With prior art communication stations it is customary to send either the actual desired signal, i.e., a ringing signal for ringing tone, or a flashing voltage for lamp flash control, or a series of data bits with each bit position corresponding to a particular lamp or ringer. Thus, the digital "word" 0101 would send a high voltage to lamp 1, a low voltage to lamp 2, a high voltage to lamp 3 and a low voltage to lamp 4. The next word could be a 0001 which would again send the high voltage to lamp 1, and lows to lamps 2, 3, and 4. Lamp 3, which has been on, would thus go off. By varying the 1's and 0's, the lamps and flash rates can be controlled. Each frame of 1's and 0's must arrive fast enough so that the station user does not observe a flashing lamp when in fact a series of 1's (steady on) is intended.
This same problem occurs when a button at the station is depressed and a stream of 1's are generated for delivery to the main processor. The stream continues while the user continues to depress the button and this depression time can vary significantly between users. Under this condition a user who depresses a button for a long period will require repetitive transmission capability of that fact and the system must not only be designed to handle this transmission but be able to process the data bits to determine precisely what has occurred at the station.
Such an arrangement, while working effectively for certain size systems, has a limitation when large amounts of data must be sent to a communication station or when there are a large number of stations served by the main processor. The trend in communications is to provide increasingly more information to the user by displaying, for example, the telephone number of a calling party. If all of this information had to be constantly repeated in 1's and 0's the processor would soon become overloaded or the service seriously degraded.
Another problem presents itself when it is desired to control both data and voice communication from a single terminal over a single line. An example of such an arrangement is shown in copending concurrently filed patent application of R. J. Nici, J. B. Sharp, and G. W. Schramm, Ser. No. 464,058, filed Feb. 4, 1983. Data communication usually consists of a short burst with the connection established automatically by a computer. In these situations it is highly undesirable and uneconomical for the computer to wait while the information pertaining to a voice call to or from the same terminal is communicated. By way of illustration if a calling party (voice) is dialing a number the outgoing message stream could possibly take several seconds to complete. If, at the same time, the computer sharing the same terminal and same line were to try to establish a calling connection had to wait until the voice call dialing interval was completed valuable time would be lost. Clearly, therefore, a need exists in the art for an arrangement of dual interspersed signaling from the same station over a common transmission line.
In copending patent application of Baugh-Smith, Ser. No. 341,840, filed Jan. 22, 1982, there is shown an arrangement for using two time separated channels for transmitting information over a single line. The Baugh et al application also shows that a multiplexed channel can be used to provide bursty data. This signaling channel, called the S channel, can be used to provide signaling information to and from the communication set. Thus, assuming a communication set using two information fields (I fields) to control separate information i.e., voice and data, and assuming a single S channel having a limited per frame bit capacity, it becomes a challenging problem to provide the necessary real time control for each of the information channels without resorting to separate S channels for each information channel.